The invention generally relates to variable-speed spinners employed in depth profiling fragile blanks of SIO.sub.2, herein referred to as silicon "chips" utilizing an etchant, and more particularly to an improved head for a high-speed spinner characterized by a negative pressure or vacuum chuck adapted to support a silicon chip as a high-angular velocity is imparted to the head during the performance of profile etching processes.
In the profiling of silicon chips utilizing an etchant, the processing frequently requires formation of steps having dimensions in the ranges of tens of angstroms with a precision of .+-.1 A. To accommodate such precise profiling, a variable-speed spinner is employed for angularly displacing the workpiece at an angular rate of 2,000 to in excess of 100,000 RPM. Consequently, the chuck employed for supporting the workpiece must be capable of securing the workpiece to the head of the spinner at high-angular rates of rotation, without fracturing or otherwise damaging the chips.
To accomplish the desired results, a negative pressure sample holding block, herein referred to as a "vacuum chuck" has been provided.
During the course of a preliminary search conducted for the invention, hereinafter more fully described, the following patents were discovered:
______________________________________ 3,389,682 L.D. Gardner June 25, 1968 3,730,134 Kadi May 1, 1973 4,024,835 Scheu et al May 24, 1977 4,184,292 DeFazio et al January 22, 1980 ______________________________________
It is believed that the high-speed vacuum chuck disclosed by U.S. Pat. No. 3,389,682 comprises the most pertinent prior art discovered in the course of the search. However, it also is believed to be abundantly apparent that this device necessarily is incapable of performing the functions required by those engaged in the etching of profiles in silicon chips utilizing high-speed spinners.
It is therefore the general purpose of the instant invention to provide a head for a vertically oriented, high-speed spinner having a vacuum chuck particularly suited for protectively and securely supporting fragile objects, such as silicon chips, and the like, as they are rotated at high angular rates.